One reason I didn't go for the Dynaudio (apart from not being able to compare it with the base system at my dealer) was that I was concerned it'd drain the battery down too quickly when used on site (this was before I knew about the irritating auto-off audio system :headwall ).
Here was my thinking at the time (apologies for any naive understanding of how things actually work

):
To drain 30Ah from the 61Ah battery (these figures are doubtless unrealistic, but you get the idea):
RCD310: 80W amp/12V = 6.6A = 4.5h at max - so 18h for 25% load
Dynaudio: 640W amp (probably peak) - so /12V = 50A = 0.5h at max - so 2h for 25% load
CONs
High risk: the more powerful amp would inevitably drain the main battery more when parked without a hook-up.
High risk: may add delay to the build time.
High risk: very little information - a risky option as no-one seems to be able to maintain them.
Medium risk: not listed as a factory option in 2011/4 price list, but is in 2011/9 (at £1250).
PROs
Medium risk: How much would it cost to add it (or something similar) later? Probably more than £1250 inc labour, and it would mean discarding (wasting) the VW speakers.
INFO:
It's listed in German Cali 2011/11 brochure as:
"10 precise matched tweeters and mid-bass tone speakers [no sub]
paired with a 10-channel amplifier for powerful sound,
with an incredible 600 watts of power.
Compatible with RCD310, RNS315 and RNS510."
This current/old Dynaudio page says of the "Multivan" installation:
"The Dynaudio sound system features a 10 channel digital amplifier with 640 watts of power driving 10 Dynaudio premium loudspeakers."
"To enable maximum sound quality and optimum performance to be experienced at every seat, sophisticated DSP (Digital Signal Processing)
was specifically tuned for the vehicle's large interior.""
(I thought I'd put this in a post on the
Audio Options thread but maybe I forgot or it didn't make it across from the old Proboards forum).
I'm happy with the RCD310 sound (which I'm
assuming is the same as the same as the RCD510 as they've equivalent amps) - but would love to hear the DynAudio.
Best wishes,
Steve